Method of splicing two webs in overlapping relation



1944- A. c. ROBERTSON METHOD OF SPLICING TWO WEBS IN OVERLAPPINGRELATION Filed Aug. 9, 1941 DES/REJD WIDTH TME 14/f/"6C/ C. RobertsonINVENTOR BY Wj A TTORNEYS Patented Oct. 10, 1944 METHOD or srmcmo 'rwowensiu ovnnmrmno RELATION Alfred C. Robertson. Rochester, N. Y.,asslgnor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey Application August 9, 1941, Serial No. 406,159

Claims.

The present invention relates to the method of splicing two webs inoverlapping relation, and particularly to the method of splicing twowebs of hygroscopic material which will insure a flat splice.

It is common practice to splice the ends of two or more webs of materialtogether so that they can.

Splicing the webs together has offered a number of difiiculties in thepast. The major difliculty was the tendency of the splice between twowebs to pucker, or buckle, transversely of the web. This buckling notonly results in the arc of the web breaking as it passes over thepulleys or rolls of the machine, but streaks in the coating occur wherethe web is puckered due to the fact that the coating material naturallruns to the bottom of the valleys. The result of this streaking is toincrease the amount of coated web which has to be removed in thevicinity of the splices with the result that there is a great amount ofcoated web which has to be wasted.

Therefore, one object of the present invention is to provide a method ofsplicing two webs in overlapping relation so that the splice will beflat and remain fiat until purposely ruptured.

Another object is to provide a method of forming a fiat splice which iscommercially practical and can be carried out without necessitating ashut down of the coating and drying machine.

And another object is to provide a method of forming a fiat splice whichis simple to carry out and requires little or no special apparatus.

The novel features that I consider characteristics of my invention arset forth with particularity in the appended claims. The inventionitself, however, both as to the steps necessary thereto, and additionalobjects and advantages thereof, will best be understood from thefollowing description ,of specific embodiments when read in connectionwith the accompanying drawing in which,

Fig. 1 is a partial side elevation of a splicing apparatus shown in myU. S, Patent 2,213,744,

issued Sept. 3, 1940, and showing a suitable piece of apparatusassociated therewith for treating one end of a web to be spliced inaccordance with the present invention,

Fig. 2 is a perspective view of the apparatus in which one end 01' theweb to be spliced is treated in accordance with the present invention.

' Fig. 3 is an enlarged sectional view of the apparatus shown in Fig. 2with an, end of a web to be treated shown inserted thereunto, and

Fig. 4 is a graph depicting how the dimensions of a web varies with thelength of time" during which it is dried in accordance with oneembodiment of the present invention.

Like reference characters refer to corresponding parts throughout thedrawing.

As set forth above, it has been found that when two webs of material arespliced in overlapping relation prior to being fed through a coating anddrying machine as a continuous strip that the splice buckledtransversely of the web causing the splice to rupture at the arches ofthe web in the machine and causing the coating to become streaked in thevicinity of the splice.

After an exhaustive study of this condition, I found that this bucklingof the splice is due primarily to the fact that the outer wrap of web ona fresh stock roll is in equilibrium with a different relative humidityfrom that prevailing in the region of the inner wrap on the previousstock roll to which it is to be spliced. This reasoning has beensubstantiated by direct measurements which were made of the outer wrapof a fresh stock roll and the inner wrap of a previous stock roll. Thetheory that buckling oi. the splice is due to humidity difierence hasbeen proved by a number of experiments where a web of material was cut,and spliced to itself and coated under ordinary conditions. The resultsof these tests indicated strongly that when two pieces of a web were inequilibrium with the same relative humidity that the splices were veryflat, buckling was absent, and streaking due to buckling of the splicewas negligible. I

It might be pointed out that this buckling of a splice of two webs isprevalent only when the webs are of hygroscopic material. A web ofhygroscopic material will alter in dimensions as the relative humidityof the air about it changes. Paper, cloth, cellulose derivative filmbase, etc. are examples of webs which are hygroscopic and will alter indimensions with changes in the relative humidity of air surroundingthem. While narrow webs of hygroscopic material will show no appreciablechange in width due to changes in relative humidity, with webs incheswide, which are common in coating procedures, changes in width of theweb due to different relative humidity conditions encountered have beenfound to range between .010 inch'and .040 inch. The diiference isgenerally in the neighborhood of .030 inch andis-easily perceptible bythe use of a steel scale.

- It will, therefore, be clearly understood that if a web in equilibriumwith an atmosphere havin one relative humidity is spliced in overlappingrelation with a web in equilibrium with an atmosphere having a differentrelative humidity and the two are passed through an atmosphere having arelative humidity the same as one of said atmospheres or different fromboth thereof, the two webs will vary in width by different amounts withthe result that there will be a buckling of the splice between the two.This I have found is the cause of the buckling of the splice between twowebs in the above referred to coating and drying process,

A web when it is fabricated and rolled up into a stock roll generally isin equilibrium with a very low relative humidity. If the stock roll isstored in a storage room or'moved into the unwinding room of the coatingmachine where the relative humidity is higher than that with which theweb material is in equilibrium it has been found that the outer wraps ofthe roll will in a short time swell, or increase in moisture content,until it is in equilibrium with the relative humidity of the storage, orunder-winder, room of the coating machine. It has been found, however,that no matter how long a stock roll of the web is kept in the storageroom, or in the unwinder room, the inner wraps of the roll will nevercome into equilibrium with the relative humidity of said room. This isprobably due to the fact that the inner wraps of the stock roll areusually covered at the ends with metal plates and are so tightly rolledthat the air of the room can reach the center of them only by diffusionfrom the edges of the roll. Consequently, since the outer wraps of a newstock roll will always be in equilibrium with a relative humiditydifferent from the inner wraps of a previous, or unwinding, stock roll,the two will tend to vary diflerently in width with changes in relativehumidity after they are spliced together in this condition. Thisdifference in dimensional change in the two webs will cause the splicebetween the two to buckle transversely of the web.

As a specific example, suppose a web of material when fabricated has aneffective relative humidity, or is in equilibrium with a relativehumidity, of 30 per cent. If this stock roll is then moved into theunwinder room of the coating machine the relative humidity of which isper cent, in a short time, e. g. one-half hour, the outer wraps of theroll will have come into equilibrium with this 50 per. cent relativehumidity but the inner wraps will stay at 30 per cent effective relativehumidity, or thereabouts, regardless of the time the roll remains inthis room. Now if another stock roll is moved into the unwinder room itwill be appreciated that the outer wrap thereof which is in equilibriumwith a 50 per cent relative humidity must be spliced to the inner wrapof the previous roll which is in equilibrium with a relative humidity of30 per cent. The result will be that when the spliced webs are thenmoved through the coating and drying stages in Y which the relativehumidity may be the sa e 85 that in the unwinder room, or differenttherefrom, the two webs will vary by different'amounts in width so thatthe splice will buckle.

I have found that this buckling of the splice between two webs ofhygroscopic material can be effectively overcome if the two webs arebrought into equilibrium with the same relative humidity immediatelypriorto the splicing operation. This technique can be carried out in anumber of different ways, namely, by subjecting the two webs to anatmosphere having the same relative-humidity until they are'inequilibium therewith, or one web may be subjected to an atmospherehaving a relative humidity with which the other web is in equilibriumwith.

However, I have developed a technique whereby the process of bringingthe two webs into equilibrium with 'the same relative humidity canbedone in a routine manner in the unwinder room of the coating machinewithout necessitating an I alteration in the speed of the splicing orcoating and drying operations in any way. According to my technique, theend of the web on the outside of the new stock roll is dried or broughtinto equilibrium with the same relative humidity with which the innerend of the previous stock roll is in equilibrium, or the end of theoutside lap on the new stock roll is dried until its effective rela'-tive humidity is 30 per cent instead of 50 per cent, using the figuresof the above noted example.

In the graph constituting Fig. 4 of the drawing,

the solid line shows how the width of the web being dried varies withthe length of time during which it is being dried. The dot-dash line ofthe graph shows the desired width, or the width of the web on the innerwrap 01' the previous stock roll having an effective relative humiditywhich is to be obtained. It will be appreciated that the width of ahygroscopic web will vary directly as the change in relative humiditywith which it is in equilibrium so that instead of change in width theordinate of the graph could be marked in relative humidity. The end ofthe outer wrap of the new stock roll could be dried just to the pointwhere it was the desired width, or the width of the inner wrap of theprevious stock roll, but I- have found that since a. web will morereadily increase in moisture content when exposed to an atmospherehaving a higher relative humidity than the one with which it is inequilibrium, then it will give up moisture, and a more accurate controlis obtained by drying the end of the web below the desired value andallowing it to pick up moisture from the atmosphere of the un-' winderroom. The dotted lines of the graph indicate the rate at which the webwill pick up moisture to reach the desired width, or effective relativehumidity.

In actual practice, this drying of the end of the web on the new stockroll can be effectively carried out by the apparatus shown in Fig. 1.The splicing apparatus, proper, as indicated, may be of the form bestshown in my U. S. Patent 2,213,744, issued September 3', 1940, which isparticularly adapted for splicing relatively wide webs of material inoverlapping endwise relation. The splicing apparatus per se forms nopart of the present invention but is only shown to indicate how theapparatus for treating the end of one web which is to be spliced to asec- 0nd web may be associated with the splicing member thereof to carryout the treating step in a routine manner without necessitating aslowing down of the feeding of the continuous web.

Broadly, the splicing apparatus comprises a support I on the top 2 ofwhich the ends of two webs W and W to be spliced are adapted to beplaced in overlapping endwise relation below the pressure element iii ofthe apparatus. Above the surface of the support I of the splicingapparatus there is disposed in any suitable manner, as by brackets 5. achamber 6 which is of a general tubular shape and having two spacedradially extending lips I forming a slot into which the end of the webof hygroscopic material W to be dried is adapted to be inserted a shown.The chamber 6 is close'dat both ends and is preferably equal in lengthto the width of the web W. Dry air held at the 'same temperature as thatof the web which is being unwound is forced into the chamber 6 through aconduit 8 communicating therewith, and may be distributed over thelength of th chamber by any suitable form of baffles desired, or may bedirected against the end of the web to be distributed by the force ofimpingement of the blast against the web, see Fig. 3. The end of the webW is left in the chamber 6 until it has been shrunk to a point below thedesired width, see Fig. 4, after which it is withdrawn into theatmosphere of the unwinder room in which the splicing apparatus ispreferably located and allowed to increase to the desired width, or tothe width of the end of the web W to which it is to be spliced. The airfor drying the web may be dried in any nuln-- ber of different ways. Forexample. compressed air which has been passed through a U-tube packedwith dry ice may be forced into conduit 8; or my experience has shownthat 75 pounds of compressed air which has been chilled to 40 F. is dryenough if the water is removed at the higher pressure and then the airis allowed to expand to atmospheric pressure. Inasmuch as only the endsof the two webs are in overlapping relation when spliced together, onlythat portion of the web W on the new stock roll which is to overlap theend of the other web W need be in eqilibrium with the same relativehumidity as said other web. Consequently, the chamber 6 need only besumciently large to dry the end of the web on a new stock roll asindicated in Fig. 3. After the end of the web W has come into equlibrium with the same relative humidity as the end of the web W they maybe brought into overlapping relation under the pressure element I of thesplicing apparatus and be spliced in the manner set forth in my abovenoted patent.

It will be readily appreciated from the above description that I haveprovided a novel method of splicing the ends of two hygroscopic webs inoverlapping relation so that a splice will be obtained which will remainfiat regardless of what changes in relative humidity the spliced websare subjected after being spliced. The technique disclosed isparticularly adapted for being carried out/ in a routine manner in theunwinder room of a coating machine, or other type of machine, adapted toperform one or more operations on a continuous web without necessitatinga shut down, or a slowing up. of the operations normal to such machines.The free end of the new stock roll is readily accessible and can bedried in the manner set forth during the time the last few wraps of theprevious stock roll are being Wound off. Then when the inner end of theprevious stock roll is available, the free end of the new stock roll isproperly conditioned and ready to be spliced thereto in a manner setforth in my U. S. Patent 2,213,144., issued September 3, 1940. thusrequiring no shutdown of the machine. This novel method of splicing notonly cuts down the amount of coated web heretofore wasted due tostreaking of the coating in the vicinity of the splice because oftransverse buckling thereof, but eliminates ruptures of splices duetobuckling which cause a shut down of the coating and drying machines andnecessitate a rethreading thereof.

Although I have shown and described one specific embodiment of myinvention, I am fully aware that many modifications of the same arepossible. My invention, therefore, is not to be restricted except in sofar as is necessitated by the spirit of the appended claims-- Havingthus described my invention, what I claim is new and desire to secure byLetters Patent of the United States is:

1. In the method of splicing two webs of the same hygroscopic materialin overlappingrelation, the steps of bringing the two portions of saidwebs which are to be overlapped into equilibrium with separateatmospheres having the same relative humidity, and splicing said webstogether while said portions are in such condition.

2. In the method of splicing two webs of hygroscopic material inoverlapping relation, one of which webs is in equilibrium with anatmosphere having a given relative humidity and the other of which is inequilibrium with a second atmosphere having a higher relative humiditythan the first mentioned atmosphere, the steps of subjecting said secondmentioned web to the drying action of an atmosphere the relativehumidity of which is below that of said first mentioned atmosphere, thensubjecting said web to said first mentioned atmosphere, until it is inequilibrium therewith, then splicing the two webs together.

3. In the method of splicing two webs of hygroscopic material havingdifferent moisture contents together in overlapping relation, the stepsof drying that portion of the web having the greatest moisture contentwhich is adapted to be in overlapping relation with the other with ablast of drying air until the moisture content thereof is slightly lessthan the moisture content of the other web, subjecting said driedportion of the treated web to the atmosphere surrounding the other webuntil the same is in equilibrium with said atmosphere and the moisturecontent thereof is the same as the moisture content of the other web,and splic ng the two webs together while they are in equilibrium withthe same atmosphere.

4. In the method of splicing two webs of hygroscopic material inoverlapping endwise relation and the ends of which webs that are to bespliced together are in equilibrium with atmospheres of differentrelative humidities, the steps of drying the end of the web which is inequilibrium with the atmosphere of higher relative humidity until it isin equilibrium with an atmosphere the relative humidity of which islower than that which the second web is in equi1ibrium-- with, thensubjecting the end of said web to the atmosphere with which the second.web is in equilibrium with until it is also in equilibrium with saidlast mentioned atmosphere, and splicing the two ends while they are inequilibrium with the same atmosphere.

5. In the method of splicing two webs of the same hygroscopic materialin overlapping relation, one of which webs is in equilibrium with anatmosphere having a given relative humidity and the other of which is inequilibrium with a second atmosphere having a. higher relative humiditythan the first-mentioned atmosphere, the steps of drying saidsecond-mentioned web until it is in equilibrium with the same relativehumidity as said first-mentioned web, said drying step being carried outat, a rate greater than that which would naturally occur by subjectingthe secondmentioned web to the atmosphere which the firstmentioned webis in equilibrium with, and splicing said webs in overlapping relationwhen in such ALFRED C. ROBERTSON.

5 condition.

